Nearly all photographic films, whether still-photography or motion-picture, share the same basic composition, namely an emulsion layer, containing photosensitive silver-halide particles, spread upon one side of an acetate base material. In either negative-image or positive-image films, and in all still-photography or motion-picture film formats, this basic emulsion layer/acetate base composition is essentially the same.
Since films are designed to project an image as light passes through them, it is important to the quality of the projected image that the film surface be free of contaminants. Some of the commonest contaminants are dust, lint and fingerprints. It is especially crucial to remove these contaminants from negatives, which must serve as masters for potentially numerous positive-image prints.
Certain chlorinated solvents have proven themselves the most effective photographic film cleaning agents because they dissolve oils well and then evaporate quickly. These characteristics reduce the need for repeated buffing of the film, whether to remove contaminants or to dry unevaporated cleaning agents. The most widely used solvent for cleaning photographic films, both privately and commercially, is the chlorinated solvent 1,1,1-trichloroethane, through processes that may be either manual or mechanized. Because of its harmfulness to the ozone layer, however, 1,1,1-trichloroethane is currently being eliminated from the film-cleaning market, both retail and wholesale. No other solvent as effective for cleaning film as 1,1,1-trichloroethane has been introduced as a replacement. There is thus a need for an effective replacement for 1,1,1-trichloroethane that is not harmful to the ozone layer.